In recent years, printers, analogue copiers, digital copiers and printing machines on the basis of electrophotographic, ink-jet or thermal transfer processes have been widely popularized, thus extremely great amounts of paper have been consumed for recording media. The paper, which being typically used for the recording media, is made of renewable pulp produced from wood.
However, large amounts of energy are consumed in various paper producing steps such as pulping steps to extract cellulose fibers from wood and paper-drying steps to dry the resultant paper. A part of these steps have been innovated to reduce CO2 amount by way of making use of biofuels such as black liquor, which being a pulp-extract residual matter, in place of fossil fuels; however, all of these steps cannot make use of such biofuels.
CO2 gas emitted from fossil fuels is believed to cause warming of earth, and also depletion of fossil fuel sources and environmental protection are serious problems, which demand to reduce the consumed quantity of paper. Saving of fuel may lead to an effective fuel utilized for other than paper production, even when the fuel being a biofuel. Recently, destructive lumbering for paper making seems to be on a decline; however, all of paper cannot be of wood from well-controlled forests; thus it is an important social problem to protect forests and to prevent deterioration of global environment through suppressing the consumed amount of paper.
In addition, paper typically contains inorganic ingredients free from burnout and decay, thus disposed paper generates waste product to be landfilled in a certain rate. However, places for waste products are definitely limited and restricted, thus the reduction of consumed amount of paper is desired also from the viewpoint of such a social issue.
In order to address these problems, paper has been conventionally reused in a way, for example, that used information recording paper is collected, the collected paper is decomposed once into pulp in paper making plants and then reproduced into paper.
However, these processes require approximately equivalent energy with those starting from fresh pulp since other energy is necessary for collecting/transporting, repulping and paper making even though new wood source being unnecessary.
In addition, the rate of recycled pulp is typically limited to about 30% for high-quality paper of information recording paper in order to prevent such quality problems as low stiffness, less whiteness and bleeding at printing.
As such, it is necessary in order to produce high-quality information-recording paper with higher whiteness that the rate of recycled pulp is limited and the pulp is produced from recycled waste paper, which possibly resulting in a cost higher than that of the processes from fresh wood in some cases. Furthermore, collection and regeneration of recording media with recorded information may cause problems in terms of preservation of secret and privacy since the recording media with recorded information are put into circulation from offices or houses.
In order to address these problems, various processes are proposed to reuse recording media in a way that images, on once-used recording media, are erased to generate the recording media. For example, such a process is proposed that a plastic, metal, paper with no liquid-permeability, or ceramics is employed as the recording medium, then a hot-melting peeler is interposed between hot-melting images and the recording medium, and the images are peeled away through heating the hot-melting peeler (e.g. see Patent Literature 1). An image erasing apparatus is proposed in which images, formed on a recording medium treated with a release agent, are transferred and peeled away by use of an endless belt having a hot-melting resin on the surface (e.g. see Patent Literature 2). An erasable paper is proposed in which images on a sheet or regular paper, prepared by coating and drying a silicone sealing agent on a coat paper, is removed through attaching and peeling a tape (e.g. see Patent Literature 3). Patent Literature 3 describes an erasable paper with a mark or an expression for mechanically distinguishing from regular paper, in order to prevent erroneous disposal due to confusion between the erasable paper and regular paper or to avoid erroneous treatment of regular paper with image erasing devices, in which the mark may be applied by printing or handwriting and the expression may display to be erasable by means of perforations.
The recording media, described in the Patent Literatures, have a base material formed of plastics, contain a silicone sealing material as an image-repellent agent, or utilize a commercially available adhesive tape.
In cases of recording media having a base material formed of plastics, users are occasionally beaten by an electrical shock since the materials tend to accumulate electrical charge during transferring steps in electrophotographic processes and the electrical charge hardly dissipates from the materials even after the transferring. In addition, plastics are typically more expensive than paper.
Patent Reference 4 etc. a utilization of silicone compounds for an image-repellent agent in order to make easy the image removal. It will be certain that the silicone compounds in the recording media make easy to remove images formed on the recording media by transfer with heat and pressure, even without coating a repellant agent on the recording media.
However, silicone compounds are considerably expensive, thus the recording media containing silicone compounds as the image-repellent agent will suffer from higher production cost. Furthermore, silicone compounds typically decrease image-fixing ability excessively, thus there may arise such problems that image-quality degrade due to offset at image formation, image-forming materials drop out from the recording media in use, which making images illegible and/or polluting the surround. In addition, it is difficult to record onto recording media, on which silicone compounds being coated, by use of water-based pens or oil pens; it is difficult to coat aqueous liquids since silicone compounds are not water-soluble.
The present inventors et al. have proposed a reusable recording medium comprising an image-repellent agent of acrylic ester or methacrylic ester polymers having fluorinated alkyl groups (e.g. see Patent Literature 3). However, employment of fluorinated polymers possibly suffers from similar problems as those of silicone; that is, fluorine compounds are likely to be expensive, which makes the cost of recording media higher. The fluorocarbon compounds typically provide excessive image-repellent effect, thus it is difficult to control fixing ability of image forming materials onto recording media, more specifically, it is difficult to assure fixing ability of recording media since fluorocarbon resins tend to excessively decrease the fixing ability of image forming materials and/or it is difficult to record onto recording media by use of water-based pens or oil pens. Furthermore, the fluorocarbon compounds described in Patent Literature 5 are insoluble in water and hardly soluble in usual organic solvents, and halogen-containing solvents are necessary for the coating, which causes an environmental problem.
The present inventors et al. have also proposed a recording medium containing an image-repellent agent that is comprised of a fluorocarbon compound, a silicone compound, an alkyl group-containing surfactant (e.g. see Patent Literature 6). However, employment of the fluorocarbon compound and/or the silicone compound causes problems similar with those described above. In some cases, toner-repellent agents containing an alkyl group may remove image forming materials; however, there exist such problems as the fixing ability of image-forming materials is unstable and/or the peeling of image-forming materials is insufficient, since the surfactants are of monomolecular with small molecular weights, thus the surfactants tend to migrate into peeling members, image-forming materials, and/or recording medium, therefore, the amount or rate of image forming materials-repellent agents is changeable.
The present inventors et al. have also proposed a method for removing image-forming materials, in which a water-containing liquid is impregnated into paper with images formed by electrophotographic processes, the paper and a peeling member are contacted and pressed while being hated in a condition that the adhesive force between the paper and image forming materials is week, then the hot-flexible image forming materials are peeled away by use of paper (e.g. see Patent Literature 7). This method is advantageous in that transferring and peeling may be carried out under lowered adhesive force since a shear force generates between water-swelling paper fibers and non-swelling image forming materials.
However, when this method is applied to conventional regular paper, the image forming materials are often incompletely removed due to occasionally higher adhesive force between image forming materials and paper, and/or a part of paper often is peeled away along with the image forming materials. It is also troublesome in that the addition of water tent to cause wrinkle or curl and then paper jam under repeated usage in image-forming apparatuses and/or image erasing apparatuses even when the additional water being a small amount. Addition of much water requires much energy to evaporate the water and leads to size change of regenerated recording media.
The present inventors et al. have also proposed a recording medium in order to solve the problem in the methods for removing image-forming materials on recording media through impregnating a water-containing liquid as described in Patent Literature 7 etc., in which the adhesive force with toners is controlled by applying compounds with an alkyl group such as alkyl ketene dimer onto a surface of recording media thereby to control the contact angle with liquids having a surface tension equivalent with that of toners (e.g. see Patent Literature 8). In the Patent Literature 8, the adhesive force with image forming materials is reduced by use of a synthetic sizing agent such as alkyl ketene dimer. This proposal is premised on that additional water can weaken the adhesive force between image forming materials and the recording media in the removal of the image forming materials. Therefore, it is difficult to apply the recording medium, disclosed in the Patent Literature 8, to image-erasing processes without adding a water-containing liquid as image-erasing promoting liquid since the adhesive force is excessively strong.
Furthermore, the alkyl ketene dimer of sizing agent described in the Patent Literature 8 is monomolecular compounds having a melting point of 40° C. to 70° C.; therefore, the higher temperatures at the processes for erasing image-forming materials and/or in image-forming apparatuses melt the alkyl ketene dimer and promote the migration thereof into peeling members, image-forming materials, and/or recording media, consequently, the amount or rate on the surface of recording media is unstable. Accordingly, repeated usage thereof often leads to unstable fixing ability or difficult peeling of image forming materials, decrease of friction coefficient in the recording media, or difficult transportation of the recording media. Furthermore, the alkyl ketene dimer applied on the recording media often moves to paper-feeding rollers of image forming apparatuses or image erasing apparatuses, which making difficult to transport the recording media. In addition, Patent Literature 8 describes that styrene, olefin or acrylic polymers may be used as a surface sizing agent other than the alkyl ketene dimer; however, there is no descriptions in terms of specific molecular structure of these polymers or excellent effect over the alkyl ketene dimer.
Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 01-297294 (Japanese Patent (JP-B) No. 2958772)
Patent Literature 2: JP-A No. 04-64472 (JP-B No. 2584112)
Patent Literature 3: JP-A No. 04-67043
Patent Literature 4: JP-A No. 10-319620 (JP-B No. 3690063)
Patent Literature 5: JP-A No. 06-219068 (JP-B No. 3222613)
Patent Literature 6: JP-A No. 10-74025
Patent Literature 7: JP-A No. 07-13383 (JP-B No. 3345472)
Patent Literature 8: JP-A No. 08-286579